Demographic Impact of HIV/AIDS
Nicolas Brouard
Institut National d'Etudes Démographiques, Paris, France
According to UNAIDS, an estimated 21.8 million persons were living with HIV/AIDS in 1996. This figure consisted of 14 million infected people in sub-Saharan Africa; 4.8 million in Asia; 1.3 million in Latin America; 700,00 in North America; 470,000 in Western Europe; 270,000 in the Caribbean; 200,000 in North Africa and the Middle East; 48,000 in North and South Pacific; and 30,000 in Eastern Europe. Sub-Saharan Africa has experienced the fastest growth in HIV infections, but projections show that it will be soon surpassed by Southeast Asia, although data for this forecast is random and difficult to collect.
Some basic properties of the dynamic of the HIV spread include: (1) the difficulties of projections that are inherent to the transmission dynamic of the virus; (2) the necessity of data which considers HIV prevalence by age and sex, information which will help to better understand the trend of the epidemic; and (3) the impact of AIDS deaths and vertical transmission on life expectancy and growth rate by modeling.
Difficulties of Demographic Projections
Understanding why projections of HIV prevalence are unreliable is instructive. Actual trends of the epidemic are often unknown in the regions most affected by HIV. Statistical data on the prevalence of HIV or on AIDS cases are too few and unreliable to authorize even a short-term prevision, and therefore, the demographic impact of the AIDS epidemic is often unknown.
Moreover, the reproduction process of the HIV epidemic population resembles the reproduction of the general human population. The incubation time, or time since infection, can be considered the reproductive period when the genes can be passed on (i.e., the viral genes can be transmitted from the primary case to the secondary case). When this process is extrapolated to many people or cases, it is like population growth except that the secondary cases are increasing much faster than birth (every month or year rather than every 27 years). With the replacement level being every month, the HIV epidemic is growing very fast, and thus, very difficult to forecast. Since HIV can have a long incubation time of 10 years, the risk of transmission remains. Even if new cases of HIV could be prevented, there would still be many people living with the virus.
Impact of AIDS on Life Expectancy
In Africa before the AIDS epidemic, half of the population died between 60 and 65 years of age. With an HIV prevalence of 15%, life expectancy decreased by an average of 15 years. The probability of death before and after the AIDS epidemic can be modeled. The survival function decreased fast and early because it was affecting the reproductive age and because of vertical transmission. However, the population growth continued to be very high. The probability of survival for a newborn before and after AIDS is given in Figure 2.
Impact of Vertical Transmission
Reduction of the transmission of HIV from a pregnant woman to her baby is a major challenge. The AIDS Clinical Trials Group (ACTG) 076 proved that the use of zidovudine reduced that transmission from 26% to 8%. Assuming that the new clinical trial in North Thailand will reduce transmission by the same amount, some consequences for childhood were examined.
Using actual demographic and epidemiological data in North Thailand, where HIV prevalence among pregnant women is estimated at 5%, the probability for a newborn to die before age 10 will drop from 54.30 per thousand to 47.10, while the probability to die from AIDS will drop from 13 per thousand to 4. This is a major issue for health services in charge of HIV-positive infants. The total number of orphans at age 10 will only slightly increase from 9.28% to 9.86%.
The life expectancy at birth in the region is expected to increase from 61.74 years to 62.3. Only a massive reduction of the prevalence will reduce a projected loss of 6.7 years of life expectancy at birth if the epidemic remains at this high level in North Thailand. Therefore, not only does vertical transmission need to be reduced but also the prevalence of HIV-infected women must decrease, so that life expectancy can return to age 69 before the onset of AIDS.
Epidemiology of HIV/AIDS in Southeast Asia and Thailand
Wiput Phoolcharoen, MD
Ministry of Public Health, Nonthaburi, THAILAND
The number of new HIV infections among adults aged 20 to 49 peaked in industrialized countries in 1983 to 1984 and then decreased. At the same time, the number of new cases in sub-Saharan Africa peaked in 1992 with close to 0.9% of the adult population infected. In Asia and the Pacific, the incidence has been increasing since 1987 and 1988 but has yet to peak; it was more than 0.1% per year in 1993 and 1994. The annual number of HIV commercial sex workers (FCSWs), based on two groups (brothel and indirect), continued to increase. Median HIV seroprevalence in males attending STD clinics declined slightly and peaked in 1994 at around 8%. These three groups comprise the high risk groups with the highest prevalence.
Among new military conscripts in the Royal Thai Army, the HIV prevalence peaked in 1993 at 3.7% and decreased by half (1.9%) in 1996. Two changes in the sexual behavior of the military conscripts in northern Thailand can be noted: (1) decrease in the number of visits to FCSWs in the past year from 57.1% in 1991 to 20% in 1995, and (2) increase in the condom use from 61% to 92.6%. Median HIV seroprevalence in pregnant women increased from 0% in 1990 to 2% in 1995 but declined after 1995 to 1.7%.
Based on cases reported between 1984 and 1996, the male-to-female ratio of AIDS decreased from 6.57:1 from 1984 to 1992 to 4.06:1. This ratio may already be 1:1 if the long incubation period was taken into account.
Projected Impact of AIDS in Thailand
The annual health impact of AIDS was estimated and projected based on baseline scenarios in Thailand from 1990 to 2010. The 70 to 80 thousand cases of adult AIDS deaths by 2010 will have a tremendous impact on the health care system. AIDS orphans less than 10 years old, estimated at more than 20,000 per year after the year 2000, will become a social burden in the next decade and century. This prevalence is high but the number of HIV-infected infants can be reduced if HIV transmission is prevented.
The HIV/AIDS Epidemic in the North: Epidemiology and Public Health
Vallop Thaineua, MD, MPH
Ministry of Public Health, Nonthaburi, Thailand
The WHO Global Program on AIDS estimated that by December 1996 there would be 30 million HIV infections and 8.4 million AIDS cases in the world.1 A rapidly increasing rate has been observed in Southeast Asia. In Thailand, the first AIDS case was diagnosed in 1984 in a homosexual who contracted HIV during his studies abroad.2 Antibody to HIV was first detected in 1985 in one of 101 male prostitutes in Bangkok.3 Since then, the HIV/AIDS epidemic has spread among homosexuals, intravenous drug users, female commercial sex workers (FCSW), promiscuous males, and later to housewives, youths, and children.4
Situation in the Northern Part of Thailand
There are six provinces of Region 10 in the northern part of Thailand, namely Chiang Mai, Chiang Rai, Phayao, Lamphun, Lampang, and Mae Hong Son. HIV prevalence and reported AIDS cases in Region 10 are the highest in Thailand. HIV antibody was first detected in thalassemic patients in 1987 in Chiang Mai.5 Female commercial sex workers in Chiang Mai first tested positive for HIV antibody (1/472) in February 1988.4 In June 1989, HIV sentinel serosurveillance of FCSWs in Chiang Mai revealed a 44% infection rate and alerted the government to implement an intensive prevention and control program.6 A high rate of HIV infection was also observed among men who attended STD clinics (10%) in 1989.
Reported AIDS cases for the six provinces in the northern part accounted for about 40% of total AIDS cases in Thailand.6 The rapid increase in the number of AIDS cases was also observed among women and children both in the northern part and the nation. As of December 31, 1996 in Thailand, there were 13,324 and 3,657 reported cases of AIDS and symptomatic HIV infection among women and children under five years, respectively. In the six northern provinces, as the male-to-female ratio decreased from 8:1 in 1989 and 1992 to less than 5:1 in 1996, the number of AIDS cases among women increased from seven cases to 6,294 cases from 1990 to1996.6 Among children less than five years old in Region 10, 1,762 cases of AIDS and symptomatic HIV infection were reported by the end of 1996. In Lampang, AIDS has become the leading cause of death since 1995, with 18% of infant deaths attributed to HIV infection.8 It is projected that there will be 200,000 cases of HIV infection, 70,000 AIDS cases, and 9,000 pediatric AIDS cases by the year 2000 in the six northern provinces of Thailand.
HIV infection among pregnant women in the North is higher than the national average. The sentinel serosurveillance of the six northern provinces, conducted every six months, revealed that the median HIV infection among pregnant women increased from 0% in June 1989 to 7.5% in June 1995 and then decreased to 5.2% in June 1996. The same trend was observed in three provincial hospitals where most of the pregnant women were tested for HIV. The rate of HIV infection among 21-year-old males started to decrease earlier, beginning in 1993, compared with pregnant women whose rate of infection started to decline in 1995.
The perinatal transmission rate in the North is around 37 to 45%. In Phayao Hospital, 71% of HIV-positive women were primigravida, and 25% of the husbands were HIV-negative (discordant couples). In Lampang Hospital, HIV infection rates among pregnant women are higher in antenatal clinics than in delivery rooms, suggesting a potential increase in mother-to-child transmission. However, in Chiang Rai Hospital, after the introduction of bottle feeding for infants born to HIV-positive mothers, the perinatal transmission rate decreased from 42% to about 25 to 30%. The proportion of infants born to HIV-positive mothers who completed the 1.5-year follow-up program increased from 62% to 81%.
Response to the HIV Epidemic among Women and Children
Information about the HIV/AIDS epidemic has been given directly to the community since the disease was first detected. Various agencies from both public and private sectors gathered to join efforts. The Upper North AIDS Control Center was set up in 1993 to formulate guidelines and facilitate their implementation. Fear of the hospital's inability to meet the increased demand to provide medical care was alleviated when the community learned how to accommodate the problem. At present, prevention of HIV transmission to women and their children has been given high priority. Target groups include single youths, housewives and husbands, pregnant women, family planning clients, and students.
The continued provision of information, education, and communication is necessary to alert people about AIDS. Promotion of desirable behaviors and family should be introduced and integrated into the learning process of primary school. Life skills education for the youths, particularly communication skills for females and responsibility among males, is useful for them to cope with sexual stimuli and negative environments. Education and counseling services for unmarried pregnant women have been provided in all community hospitals and a number of health centers. Promotion of condom use with convenient access is another strategy aimed at inexperienced youths in sexual relationships. Better antenatal care and
ZDV prophylaxis in HIV-positive pregnant women, along with safe bottle feeding, are undertaken in community hospitals. This integrated approach is being introduced to the target groups with respect to local beliefs and culture. More importantly, community participation is emphasized in order for AIDS prevention strategies to be successful and sustainable.
Lessons Learned from the HIV Epidemic in the North Thailand
HIV prevention and care must be done with the alliance of various organizations and in a concerted effort. A comprehensive approach is needed to cope with multiple problems, including medical, psychological, social, and economic problems. Communities have to be strengthened and become involved. Information and education about AIDS should be adapted for cultural acceptance. A constructive international collaboration will help the world conquer HIV.
References
1. World Health Organization. HIV/AIDS: The global epidemic. Wkly Epidemiol Rec 1997; 72:17-20.
2. Limsuwan A, Kunapa S, Siristonapun Y. Acquired immunodeficiency syndrome in Thailand: A report of two cases. J Med Assoc Thai 1986; 69:164-69.
3. Wangroongsarb Y, Weneger BG, Wasi C, et al. Prevalence of HTLV-III/LAV antibody in selected populations in Thailand. Southeast Asian J Trop Med Public Health 1985; 16:517-20.
4. Weniger BG, Limpakarnjanarat K, Ungchusak K, et al. The epidemiology of HIV infection and AIDS in Thailand. AIDS 1991; 5(suppl 2):S71-85.
5. Thongkrajai P, Chanarat P, Kulapong P, et al. Epidemiological assessment of antibodies in Thailand. Southeast Asian J Trop Med Public Health 1988; 19:579-84.
6. Ungchusak K, Sriprapandh S, Pinichpongse S, et al. First national sentinel seroprevalence survey of HIV-1 infection in Thailand, June 1989. Thai AIDS J 1989; 1:57-74.
7. Division of Epidemiology. AIDS situation as of 31 December 1996. Wkly Epidemiol Surv Rep 1997; 27(suppl 12):S150-67.
8. Lampang Provincial Health Office. Annual report fiscal year 1996. Lampang, Thailand: Ministry of Public Health, 1996.
9. Department of Communicable Disease Control. AIDS situation in the region 10. Nonthaburi, Thailand: Ministry of Public Health, 1996.
HIV Variation: Epidemiological, Clinical, and Public Health Implications
Max Essex, DVM, PhD
Harvard AIDS Institute, Boston, USA
Variation of the human immunodeficiency virus (HIV) has implications for the epidemic in Southeast Asia. What makes this virus different from other viruses is its greater variability, high mutation rate, ability to alter resistance to drug treatment, and ability to be transmitted.
HIV-1 vs. HIV-2
An entire study among the same cohort of commercial sex workers (CSWs) revealed the interval-specific incidence of HIV-1 and HIV-2. HIV-1 was found to be more efficiently transmitted heterosexually than HIV-2, with the incidence of HIV-1 rapidly overtaking that of HIV-2 by 1990, even though HIV-1 entered the scene later. The seven year Kaplan-Meier survival curve for this cohort of seropositive CSWs showed that HIV-2 was less lethal than HIV-1 in terms of disease-free survival without progression to AIDS. The death rate due to AIDS after the time of initial conversion was higher for HIV-1 than for HIV-2.
HIV-1 Clades
HIV-1 variations are 40% to 50% related to each other but produce different outcomes in terms of transmission efficiency, epidemiological potential, disease development, and natural history. The high rate of mutation for HIV-1 gives rise to a high error rate at one nucleotide per genome in a replication cycle. The largest number of mutations are observed in the outer gp120. The accumulated envelope gene variation is 10% per year. (Both HIV-1 and HIV-2 are less than 100 years old in humans.)
The evolution of HIV-1 subtypes or clades are not known but it is generally accepted that they come from Africa. HIV-1 clades A through E are well-characterized in different areas of the world with two million infections each worldwide. The heterosexual epidemic is maintained through the transmission genotype in clades A, C, D and E; however, clade B has lost its "transmission" genotype (i.e., counterselection).
The trends projected for each subtype are different; E and C are estimated to be the most prevalent now and in the future. In Southeast Asia, the dominant clade is E, with three to five million people infected and more infections expected, while clade B is plateauing in the United States, Europe and South America. Over 90% of the infections through subtypes A, C, D and E are associated with heterosexual transmission, while B is associated with homosexual transmission and intravenous drug use. For instance, subtype E taken from Thailand as well as subtype C from India replicated more efficiently in Langerhans' cells than subtype B taken from homosexuals in Boston (Table 1).
Clade differences also exist in terms of progression to AIDS. In comparing clade A and non-clade A survival curves, some clades showed different characteristics for transmission efficiency and disease development. Fewer cases of AIDS development or seroconversion were found in clade A than in non-clade A within the same HIV-1 cohort. Therefore, some clades are more aggressive in seroconversion than others.
When DNA sequences of viruses were compared between different countries, clade C in Botswana displayed the most genetic variation, more than the same clade found in Zimbabwe and India. Subtype E in Thailand and B in the United States were less diverse genetically. Divergence between clades was based on neighbor-joining analyses.
With regards to intra-clade differences, E and E subtypes have a high degree of similarity and low differences, while the opposite is true for C and C subtypes. Therefore, whatever intervention is implemented for clade E, there will be more control of analysis of outcome in the same set of population. Furthermore, clades C and E have significant differences which have implications for the rate of transcription and transcriptional activities.
Conclusion
HIV is not one simple single virus. It has many subtypes and varies at a high rate even within subtypes. Inter- and intra-subtype differences mean that certain strains of HIV spread and cause disease faster or slower than others, with possible implications for the rate of transmission from mother to infant. The rate of mutation varies dramatically due to the higher rate of replication or possibly error rates, causing the virus to evolve drug resistance as well as other properties of transmission and disease development at a higher rate.
Though much has been learned about HIV and about how to prevent or control this virus, many hurdles remain because of the high rate of mutation and variation. Current interventions may be less fruitful due to future adaptations of the virus to the population. Observations seen in one part of the world today could serve as a warning for potential changes that could result in other regions of the world tomorrow.
